Indonesian Geotechnical Journal

Three-Dimensional Soil-Structure Interaction Analysis of Top-Down Basement Excavation in Jakarta Soft Soil Condition Considering Numerical Instability

2026-06-08T07:58:31+00:00

Basement construction in dense urban areas with soft clay deposits requires excavation support system capable of controlling ground deformation and retaining structure responses during staged excavation. This study evaluates the behavior of a top-down excavation system in Jakarta soft clay using three-dimensional finite element modelling with a soil–structure interaction approach. The numerical model was conducted using MIDAS GTS NX and consisted of soil layers, a diaphragm wall, ring slabs, a raft foundation, kingposts, bored piles, and soil–structure interface elements. The soil was modeled using the Hardening Soil Model, while the structural components were modeled as linear elastic elements. Soil parameters were interpreted from borehole data, Standard Penetration Test results, Cone Penetration Test results, and laboratory tests. The results show that the lateral displacement of the diaphragm wall increased with excavation depth due to the release of lateral earth pressure on the excavated side. A fully converged response was obtained up to the Basement 3 excavation stage, with a maximum diaphragm wall displacement of 9.77 mm, corresponding to approximately 0.10% of the excavation depth. The representative vertical displacement section showed a surface settlement of approximately 6 mm and an upward movement of approximately 16 mm at the excavation base, indicating a basal heave tendency without confirmed basal failure. Principal stress and maximum shear stress distributions showed stress concentrations around ring slab elevations, slab openings, and diaphragm wall corners. These results indicate that the ring slabs acted not only as floor elements but also as lateral restraint members that contributed to stress redistribution and wall deformation control. The subsequent excavation stage experienced numerical non-convergence, which was interpreted as a numerical failure or a sign of local instability rather than a confirmed global stability failure. Overall, this study highlights the importance of three-dimensional soil–structure interaction modelling for evaluating top-down excavation behavior in soft clay.

Derivation of Elastic Parameters from Integrated Seismic Refraction Tomography and Multichannel Analysis of Surface Waves (MASW) for Geotechnical Site Characterization at APT Pranoto Airport, Samarinda, East Kalimantan

2026-07-13T01:14:23+00:00

APT Pranoto Samarinda Airport is a transportation infrastructure facility that has experienced subsidence in the taxiway area, indicating potential issues related to subsurface conditions. This study aims to determine the distribution of dynamic elastic parameters, estimate the approximate groundwater table position, and evaluate the brittleness of subsurface materials via seismic refraction tomography (SRT) and multichannel analysis of surface waves (MASW). The derived parameters include Young’s modulus, bulk modulus, shear modulus, and Poisson’s ratio. The brittleness index was used to evaluate material brittleness, while the / ratio was used to estimate the approximate groundwater table position. The interpreted dynamic elastic parameters were qualitatively compared with lithological information and standard penetration test (SPT) data obtained from nearby soil borings to support the interpretation of subsurface conditions. The results indicate that shallow layers exhibit relatively lower Young’s, shear, and bulk modulus values than deeper layers. In contrast, deeper layers exhibit higher elastic parameter values, while the brittleness index indicates a transition from relatively ductile shallow materials to more brittle materials at greater depths. The / distribution suggests an approximate groundwater table at depths of 2.5–3 m. Relatively high Poisson’s ratio values in some zones may reflect pore-fluid influence on the elastic response of the subsurface materials. However, it should be noted that Poisson’s ratio alone is insufficient to establish groundwater saturation. At depths greater than 15 m, higher elastic parameter values generally correspond to higher nearby SPT values. However, these dynamic elastic parameters should not be interpreted as direct measures of geotechnical soil stiffness. These subsurface characteristics may help explain the deformation susceptibility of the taxiway area; however, the specific cause and depth interval responsible for the observed subsidence cannot be determined from the present data alone.

Effectiveness of Spider Web Foundation Versus Raft Foundation in Resisting Static and Dynamic Loads at Liquefaction Prone Area

2026-06-01T00:21:07+00:00

As one of the earthquake-prone countries with liquefaction risk in certain soil conditions, Indonesia has developed innovative earthquake-resistant infrastructure. One of the innovations is Konstruksi Sarang Laba-Laba foundation (KSLL), literally translated as spider web foundation. The KSLL foundation system was invented by Ir. Sutjipto and Ir. Riyantori in 1976. This research compares the KSLL foundation against the conventional raft foundation in resisting static and dynamic loads. The study was based on data from University Hospital in Jember which uses KSLL as its foundation. Based on the soil investigation data, a water-saturated loose sandy soil, which is suspected to have liquefaction potential, was identified at a depth of 5-9 m. Based on liquefaction potential assessment, the study site has a high liquefaction potential with an LPI value of 27.7. Finite Element Method was used to compare the KSLL foundation against a raft foundation with equal concrete volume to the KSLL foundation. The results indicate that the KSLL foundation performs better than the equivalent raft foundation, having lower settlement under both static and dynamic loading conditions. Although higher axial forces were observed in the KSLL foundation, its overall performance remained superior. In contrast, the equivalent raft foundation developed high bending moments and shear forces, experiencing localized punching deformation. These findings demonstrate that the KSLL foundation provides a more effective foundation for structures constructed on liquefaction-prone ground by enhancing stability and reducing deformation.

Evaluating Quality of Piles Constructed in Indonesia Through Five Year of Crosshole Sonic Logging Data

2026-08-31T14:28:22+00:00

Deep foundation is one of the structural components where ensuring pile integrity is essential to achieve the required strength. Unlike columns, beams, or other structures that can be visually inspected, pile foundations require specialized tools to assess their integrity. One of the tests that can be utilized is the Crosshole Sonic Logging (CSL) test, a method that relies on wave propagation to evaluate the integrity of cast-in-place bored piles. The purpose of this paper is to analyze CSL dataset of piles constructed in Indonesia, identifying patterns and trends within large datasets. This study aims to demonstrate how database analysis can be used to evaluate the distribution of foundation quality in Indonesia and observe trends in foundation construction practices. The study is based on a CSL test dataset collected over a 5-year period (2020–2024) and includes data from 1,672 bored piles located in various regions across Indonesia, covering diverse soil conditions and construction methods. The study indicates that (1) About 30% of tested piles fall into Class B & C (piles with defects) (2) Nearly 70% of the anomalies are located at the bottom of the pile (3) Piles with a diameter greater than 1.6 m or a length greater than 75 m exhibit defects in more than 50% of cases (4) Most anomalies occur on Java Island, where 70% of the total piles are located, accounting for 82% of all piles with defects.

Field Monitoring of Secant-Pile Supported 11 m Excavation in Residual Soil: A Case Study from Bogor

2026-09-05T13:47:23+00:00

To maximize usable construction area in contoured terrain, cut-and-fill operations are often unavoidable. This paper presents a two-tier excavation, the deepest cut being 11 m + 4.7 m and the shorter cut being 5 m + 4 m. The cut was used to make space for a residential house. Subsurface investigation revealed a stratigraphy of medium silt (average NSPT ≈ 5) to a depth of 6 m, underlain by 4 m of stiff silt (average NSPT ≈ 12), and a hard silt layer extending beyond the investigation depth. The deepest excavation till mid-excavation was retained by 22 m long secant pile, while the mid-excavation till the shallowest excavation was retained by 16 m long secant pile. Excavation support was provided by secant piles: a 22 m long system for the upper excavation and a 16 m long system for the lower excavation, comprising 0.8 m diameter secondary piles and 0.6 m diameter primary piles. Pre-construction analysis predicted a maximum deformation of 2.3 cm at the top of the secant pile for the deepest cut. To ensure deformation was within limits, inclinometer monitoring was conducted daily over 12 days during excavation. Surprisingly, no measurable movement was recorded. This could be attributed to the saturated soil parameters used for analysis, whereas the soil was in unsaturated state during excavation. While adopting unsaturated parameters may yield results closer to observed behavior, such an approach is less conservative. Given Bogor’s high rainfall, conservative design using saturated soil parameters remains prudent to ensure safety, particularly in residential construction.